advance the coastline: move the coastline seaward with land reclamation (expensive)
hold the line: keep the coastline in the same place, using hard and soft engineering (expensive)
strategic retreat: allow the coastline to move inland, allowing some erosion but defending when nessisary (cheaper)
doing nothing: allow natural erosion and flooding to take place (lowest cost option)
2 of 9
Climate change on coasts
by 2100, sea levels could be 50-100cm higher
the UK may get more powerful winter storms and frequent rainfall
increased rates of erosion on cliff faces, and more frequent mass movement
deposition on spits and sand dunes
flooding of low coastal areas
3 of 9
Weathering, mass movement and sea level rise
freeze thaw is a type of mechanical weathering (water enters cracks in the rock, freezes, expands and splits it apart
chemical weathering occurs when water reacts with minerals in a rock. It dissolves the calcite in limestone, or react by hydrolysis with feldspar in granite
during heavy rainfall, cliffs often become saturated with water and water flowing inside makes the cliff weak
4 of 9
Contrasting coasts
HARD ROCK COAST:
cliffs tend to be high and vertical
beaches made up of pebbles and bolders
landforms such as caves, arches and stacks
wave cut platforms
SOFT ROCK COASTS:
cliffs are low and gently sloping
beaches of sand or mud
no stacks or stumps
wave cut platforms are unusual
5 of 9
Coast erosion
HYDRAULIC ACTION:
the force of water striking cliffs and forces air into joints and faults which fracture the rock
ABRASION:
rock and sand thrown with force against cliffs causing the cliffs to wear away
ATTRITION:
the rocks thrown against cliffs causing the rocks to be broken up
6 of 9
Concordant and discordant coasts
CONCORDANT:
parallel to the coast
same type of rock all along the length
tend to have fewer bays and headlands
Lulworth Cove
DISCORDANT:
alternate hard and soft rock
the soft rock erodes quicker than the hard rock
Swanage Bay
7 of 9
Waves and landforms
DESTRUCTIVE WAVES:
break with a steep descent with little swash so backwash is strong and erodes material
plunging waves are close together and can form rip currents which remove sand and create steeper beaches
CONSTRUCTIVE WAVES:
spill up the beach quite strongly and travel long distances
the water soaks up into the beach so the returning water is weaker
the waves tend to move sand and other materials up the beach to the land
8 of 9
How LSD forms landforms
material is moved along the coast
if there is a change of direction in the coastline this material is deposited across the bay or river mouth
the bay may eventually be closed off as the sand bar reaches the other side
the depositation will end when the current becomes too strong from a river
Comments
No comments have yet been made